Solar activity fluctuates in sync with a series of characteristic cycles. The most well-known of these is the 11-year Schwabe cycle. Naturally, 11 years are a relatively short time with respect to climate. Due to the inertia of the climate system, large climatic impacts cannot be expected from these short cycles. Yet it is still worthwhile to take a closer look. A series of appearing papers over the past years has looked into the Schwabe cycle and searched for a possible climate coupling in historical datasets. The search was fruitful: the solar Schwabe cycle has a measureable impact, and one that should not be underestimated.

We’d first like to start in Germany. Here a team of scientists led by Dominik Güttler of ETH Zürich studied 100-year old oak trees from the Medieval Warm Period in South Germany. Using C14 dating and counting tree rings, the scientists were able to find a clearly pulsating 11-year cycle. The paper appeared in January 2013 in the Proceedings of the Twelfth International Conference on Accelerator Mass Spectrometry. The abstract:

Evidence of 11-year solar cycles in tree rings from 1010 to 1110 AD – Progress on high precision AMS measurements
Oak tree rings from Southern Germany covering the AD 1010–1110 years have been analyzed for radiocarbon with accelerator mass spectrometry (AMS) at the laboratory at ETH Zurich. High-precision measurements with a precision down to 12 years radiocarbon age and a time resolution of 2 years aimed to identify modulations of the 14C concentration in tree ring samples caused by the 11 years solar cycles, a feature that so far is not visible in the IntCal calibration curve. Our results are in good agreement with the current calibration curve IntCal09. However, we observed an offset in radiocarbon age of 25–40 years towards older values. An evaluation of our sample preparation, that included variations of e.g.: chemicals, test glasses and processing steps did not explain this offset. The numerous measurements using the AMS-MICADAS system validated its suitability for high precision measurements with high repeatability.”

The next stop is Italy in the Ionian Sea. Researchers there as well found the 11-year solar cycle in the climate archives of the last 2700 years. The study was published in March 2015 in the journal Climate of the Past. The abstract:

A high-resolution δ18O record and Mediterranean climate variability
A high-resolution, well-dated foraminiferal δ18O record from a shallow-water core drilled from the Gallipoli Terrace in the Gulf of Taranto (Ionian Sea), previously measured over the last two millennia, has been extended to cover 707 BC–AD 1979.Spectral analysis of this series, performed using singular-spectrum analysis (SSA) and other classical and advanced methods, strengthens the results obtained analysing the shorter δ18O profile, detecting the same highly significant oscillations of about 600, 380, 170, 130 and 11 years, respectively explaining about 12, 7, 5, 2 and 2% of the time series total variance, plus a millennial trend (18% of the variance). The comparison with the results of multi-channel singular-spectrum analysis (MSSA) applied to a data set of 26 Northern Hemisphere (NH) temperature-proxy records shows that NH temperature anomalies share with our local record a~long-term trend and a bicentennial (170-year period) cycle. These two variability modes, previously identified as temperature-driven, are the most powerful modes in the NH temperature data set. Both the long-term trends and the bicentennial oscillations, when reconstructed locally and hemispherically, show coherent phases. Furthermore, the corresponding local and hemispheric amplitudes are comparable if changes in the precipitation–evaporation balance of the Ionian sea, presumably associated with temperature changes, are taken into account.”

In April 2014 Liang Zhao and Jing-Song Wang of the Peking National Center for Space Weather reported in the Journal of Climate on another Schwabe finding. The authors studied fluctuations in the east Asian monsoons and here too were able to see a clear influence by the 11-year solar cycle. The abstract of the paper:

Robust Response of the East Asian Monsoon Rainband to Solar Variability
This study provides evidence of the robust response of the East Asian monsoon rainband to the 11-yr solar cycle and first identify the exact time period within the summer half-year (1958–2012) with the strongest correlation between the mean latitude of the rainband (MLRB) over China and the sunspot number (SSN). This period just corresponds to the climatological-mean East Asian mei-yu season, characterized by a large-scale quasi-zonal monsoon rainband (i.e., 22 May–13 July). Both the statistically significant correlation and the temporal coincidence indicate a robust response of the mei-yu rainband to solar variability during the last five solar cycles. During the high SSN years, the mei-yu MLRB lies 1.2° farther north, and the amplitude of its interannual variations increases when compared with low SSN years. The robust response of monsoon rainband to solar forcing is related to an anomalous general atmospheric pattern with an up–down seesaw and a north–south seesaw over East Asia.”

Two months ago a team of researchers led by Zhongfang Liu published a study on the North American winter climate in the journal Environmental Research Letters. Surprisingly the scientists found a strong impact by the 11-year solar cycle, which in part has an influence on the climate of the North American winter via the Pacific circulation system. Abstract:

Solar cycle modulation of the Pacific–North American teleconnection influence on North American winter climate
We investigate the role of the 11-year solar cycle in modulating the Pacific–North American (PNA) influence on North American winter climate. The PNA appears to play an important conduit between solar forcing and surface climate. The low solar (LS) activity may induce an atmospheric circulation pattern that resembles the positive phase of the PNA, resulting in a significant warming over northwestern North America and significant dry conditions in the Pacific Northwest, Canadian Prairies and the Ohio-Tennessee-lower Mississippi River Valley. The solar-induced changes in surface climate share more than 67% and 14% of spatial variances in the PNA-induced temperature and precipitation changes for 1950–2010 and 1901–2010 periods, respectively. These distinct solar signatures in North American climate may contribute to deconvolving modern and past continental-scale climate changes and improve our ability to interpret paleoclimate records in the region.”

In the conclusion they write:

Our results have shown the influence of the 11year solar cycle on the PNA associated atmospheric circulation pattern and winter surface climate in North America.”

Also in the Bering Sea a team of scientists showed the impacts of the solar Schwabe cycle. Kota Katsuki and his colleagues found the cycle in the climate archives of 13,000 years ago. That study appeared in April 2014 in the Geophysical Research Letters:

Response of the Bering Sea to 11-year solar irradiance cycles during the Bølling-Allerød
Previous studies find decadal climate variability possibly related to solar activity, although the details regarding the feedback with the ocean environment and ecosystem remain unknown. Here, we explore the feedback system of solar irradiance change during the Bølling-Allerød period, based on laminated sediments in the northern Bering Sea. During this period, well-ventilated water was restricted to the upper intermediate layer, and oxygen-poor lower intermediate water preserved the laminated sediment. An 11-year cycle of diatom and radiolarian flux peaks was identified from the laminated interval. Increased fresh meltwater input and early sea-ice retreat in spring under the solar irradiance maximum follow the positive phase of Arctic Oscillation which impacted the primary production and volume of upper intermediate water production in the following winter. Strength of this 11 year solar irradiance effect might be further regulated by the pressure patterns of Pacific decadal oscillation and/or El Niño-Southern Oscillation variability.”

Influence of the Schwabe/Hale solar cycles on climate change during the Maunder Minimum
We have examined the variation of carbon-14 content in annual tree rings, and investigated the transitions of the characteristics of the Schwabe/Hale (11-year/22-year) solar and cosmic-ray cycles during the last 1200 years, focusing mainly on the Maunder and Spoerer minima and the early Medieval Maximum Period. It has been revealed that the mean length of the Schwabe/Hale cycles changes associated with the centennial-scale variation of solar activity level. The mean length of Schwabe cycle had been ~14 years during the Maunder Minimum, while it was ~9 years during the early Medieval Maximum Period. We have also found that climate proxy record shows cyclic variations similar to stretching/shortening Schwabe/Hale solar cycles in time, suggesting that both Schwabe and Hale solar cycles are playing important role in climate change. In this paper, we review the nature of Schwabe and Hale cycles of solar activity and cosmic-ray flux during the Maunder Minimum and their possible influence on climate change. We suggest that the Hale cycle of cosmic rays are amplified during the grand solar minima and thus the influence of cosmic rays on climate change is prominently recognizable during such periods.”

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If the 11-year cycle already has an impact, then just imagine the profound impact that the other loner term cycles have, such as the 78-year cycle and the 1000-year solar cycle. These surely cement the climate into longer term phases. -PG

5 responses to “Review By German Experts Show That Even The 11-Year Solar Cycle Has Undeniable Impact On Global Climate”

Hi from Oz. Facts: Water vapour is the major atmospheric greenhouse gas. Water is a polar molecule, which means it can be attracted / repelled by electrostatic force. The sun modulates this force (e.g. The Northern Lights). Hence the solar activity / Earth climate connection?

A polar molecule is only attracted/repelled by a non-homogeneous electrostatic field – the force is proportional to what is called a “field divergence”. A dipole in a field tries to orient itself in a direction of a field, just like a compass needle – but the compass needle does not know it it should move the whole compass north or south.

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